Extension of Zonal Fares11.2 The Franchise shall use reasonable endeavours to extend Oyster PAYG to those
areas bounded by and including the Stations located at Epsom, Gatwick Airport,
Luton Airport Parkway, Welwyn Garden City and Hertford North by 30 September
2015 provided that the Franchisee and the Secretary of State agree that the terms
of such introduction are not detrimental to the overall commercial position of the
Franchise.

hmm... the language there makes it look like a pretty weak commitment. Plus you'd have thought that it would be one of the things that they were trumpeting with fanfare on their own website if they had any intention of doing it.